Catalytic converter system for internal combustion engines



June 1, 1965 w w. GARY Re, "25,787'

CATALYTIC CONVERTER SYSTEM FOR INTERNAL COMBUSTION ENGINES Origina;Filed May 9, 1960 6 Sheets-Sheet -1 CATALYTIC CONVERTER SYSTEM FORINTERNAL COMBUSTION ENGINES Original File d May 9, 1960 W. W. GARY June1,1965

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United States Patent 25,787 CATALYTIC CONVERTER SYSTEM FOR INTER- NALCOMBUSTION ENGINES Wright W. Gary, 2317 Kimbridge Road, Beverly Hills,Calif.

Original No. 3,065,595, dated Nov. 27, 1962, Ser. No. 27,721, May 9,1960. Application for reissue May 27, 1964, Ser. No. 381,604

4 Claims. (Cl. 6030) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

The present invention relates to apparatus and methods for reducing thequantities of unburned hydrocarbons and carbon monoxide emitted from theexhaust [system] systems of internal combustion engines, and it relatesparticularly to a new apparatus and method employed in an internalcombustion engine exhaust system wherein unburned hydrocarbon and carbonmonoxide components of the engine exhaust are oxidized [by a novelcombination of direct ignition burning and catalytic oxidation] in theexhaust system.

The exhaust gases from the average automobile contain a mixture ofcarbon monoxide, carbon dioxide, unburned hydrocarbons, nitrogen, someof the nitrogen oxides, and under certain conditions, portions ofunconsumed air. It is well established that these automobile exhaustgases, and similar exhaust gases from other internal combustion engines,accumulate in the atmosphere and react to sunlight to form smog whichcauses eye irritation, is harmful to agricultural production, andappears to be a substantial human health hazard. The unburnedhydrocarbons in the exhaust gases appear to be the principal smogproducing agents, so that it is important to reduce the hydrocarboncontent of the exhaust gases to an absolute minimum. Also, although thecarbon monoxide content of the exhaust gases does not appear to be asmog forming element, it is similarly important to reduce the output ofthis poisonous gas to a minimum. As an example of the amounts ofhydrocarbons and carbon monoxide now considered acceptable for exhaustoutputs, the California Legislature has recently established a newmaximum effluent proposal of 275 parts per million of hydrocarboncontent and 1.5% carbon monoxide content in the escaping exhaust.

Prior attempts to reduce the unburned [hydrocarabon] hydrocarbon andcarbon monoxide content in the automobile exhaust have taken two forms,namely, (1) afterburners for direct burning of the undesired materialswith excess air at temperatures above 2000 F., and (2) catalyticconverters for catalytically oxidizing or burning the unwanted materialswith excess air at temperatures above about 500 F., catalytic actionpermitting such lower temperature burning. However, neither theafterburner nor the catalytic converter has heretofore proved completelysatisfactory under the Wide variety of operating [condtions] conditionswhich must be met. During idle engine operation, the volume of exhaustgases is about 6 cubic feet per minute at a temperature of around 400F., with an abnormal concentration of gasoline when the engine is firstturned on and the automatic choke is operating; while at high automobilespeeds (e.g. freeway speeds) the volume of exhaust gases will exceed 100cubic feet per minute and the temperature will range above 1300 F. Theunburned hydrocarbon concentration ranges from an average of about 600parts per million, up to about 6,000 parts per million duringdeceleration. It is diflicult to provide a satisfactory firing means foran afterburner, conventional spark plugs being subject to blowout whenthe exhaust gases are moving at high velocity, and often not properlysupporting combustion under cold engine conditions or where inadequatequantities of fuel or air are present in the exhaust gases. Often,additional gasoline must be injected directly into the exhaust systemwith afterburners to initiate or to support the combustion.

Similar difiicuities are encountered with catalytic converters. Forexample, under cold starting conditions, it often requires aconsiderable period of time before the catalyst reaches the necessary500 F. or higher (preferably 900"1000 F.), in order to operateefficiently. The relatively high thermal conductivity and heat capacityof catalysts heretofore employed caused the warm-up problem to beparticularly diflicult for catalyst [converts] converters.

Regardless of what type of anti-smog apparatus was employed in theexhaust system, it has heretofore been a particularly dificult problemin the art to provide approximately the required amount of air in theexhaust system for complete oxidation of the previously unburned or onlypartially burned exhaust ingredients, i.e., to provide approximatelystoichiometric oxidizing conditions in the exhaust system. If too littleair is present for substantially complete oxidation, then the apparatuswill fall short of its desired purpose of promoting maximum oxidation ofunoxidized or partially oxidized exhaust ingredients. On the other hand,if too much air is provided, then it will cool the exhaust and therebyrender the oxidation process less eflicient, so that maximum oxidationwill not be achieved under this condition either.

A principal reason for previous difiiculties in providing approximatelythe required amount of added air to the exhaust stream for optimumoxidation is that the air requirement varies considerably'underdifferent modes of vehicle operation, both as to absolute rate of airflow (cubic feet per minute) and as to the percentage of air added inrelation to the exhaust volume. Generally speaking, the air requirementis ufiected both by changes in engine speed and by changes in the loadon the engine at various speeds, increased engine speed usuallyrequiring more air, but at a rate not nearly proportionate to enginespeed, while increased load on the engine usually results in arequirement of less air. It will be apparent from this that under mostoperating conditions the proper amount of air will not be deliveredeither by a constant volume type of pump such as an electricallyactuated pump, or by a pump that is driven by the engine at a speedproportional to engine speed.

According to the present invention, a novel means for introducing air iscombined with the internal combustion engine and its exhaust system soas to provide approximately the required amount of added air forsubstantially complete oxidation of previously unoxidized or onlypartially oxidized exhaust ingredients under various differentconditions of engine operation, and particularly under the diflercntmodes 0) operation which are the predominant ones involved in theproduction of harmful air pollutants.

Thus, it is a general object of the present invention to provide a novelmeans for introducing air into the exhaust system of an internalcombustion engine to improve the oxidizing conditions in an oxidizingzone in the system, wherein the volume of air that is introduced variesunder difierent modes of vehicle operation so as to provideapproximately the required amount of added air for substantiallycomplete combustion of previously unburned or only partially burnedexhaust ingredients, without providing an excessive amount of air whichwould reduce exhaust temperature and decrease oxidizing efiiciency inthe oxidizing zone.

Another object of the invention is to provide a combi nation of aninternal combustion engine, its associated exhaust system with a zonetherein within which oxidation promoting conditions obtain, and meansfor introducing air into the exhaust system at a point where the airwill improve the oxidation promoting conditions in said zone, the airintroducing means including an air pump which is driven from the engineby means of a drive coupling between the engine and the pump, this drivecoupling being responsive to back pressure in. the exhaust system sothat under relatively low back pressure the coupling operates the pumpto deliver a relatively large percentage of air in relation to theexhaust volume and under relatively high back pressure the couplingoperates the pump to deliver a relatively small percentage of air inrelation to the exhaust volume, whereby the engine, its exhaust system,the air pump and its drive coupling from the engine all cooperate so asto function in a new manner, increases in engine speed causing the drivecoupling to drive the pump at increased speed so as to provide more airas required to the oxidizing zone in the exhaust system, but increasesin the exhaust back pressure from greater engine load having the efiectof loading up the air pump so as to cause a relative slowdown of the airpump and consequently a smaller percentage of air is delivered to theoxidizing zone in the exhaust system in relation to the exhaust volume.

A more specific object of the invention is to provide a novelcombination of the character described of aninternal combustion engine,its exhaust system with a zone therein wherein oxidation promotingconditions obtain, an air pump for introducing air into the exhaustsystem at a point where the air will improve the oxidation promotingconditions in the oxidizing zone, and a slip-clutch drive couplingoperatively connecting the engine to the air pump for driving the pump,slippage in the coupling being responsive to back pressure in theexhaust system, relatively low back pressure causing relatively lowslippage whereby the coupling operates the pump to deliver a relativelylarge percentage of air in relation to the exhaust volume, andrelatively high back pressure causing relatively high slippage wherebythe coupling operates the pump to deliver a relatively small percentageof air in relation to the exhaust volume, the pump speed being variedalso generally in accordance with variations in engine speed because ofthe fact that the pump is driven through the drive coupling from theengine.

The zone in the exhaust system referred to in the immediately precedingobjects wherein oxidation promoting conditions obtain may comprise acatalyst bed in a catalytic m-ufiler which forms part of the exhaustsystem, or alternatively the zone may merely be a region within theexhaust system wherein a temperature is produced'that is sufiicientlyhigh to cause direct flame ignition of the exhaust ingredients.

[In view of these and other problems in the art, it is an] Anotherobject or" the present invention is to provide a novel apparatus andmethod in an internal combustion engine exhaust system which combinesthe direct firing of a portion of the unburned hydrocarbons and carbonmonoxide with the catalytic oxidation of a further portion of theseundesirable materials in such a manner that the quantities of thesematerials released to the atmosphere are within acceptable limits forall engine operating conditions.

Another object of the present invention is to provide an exhaust systemfor an internal combustion engine which includes a case containingcatalytic material which replaces the conventional muffler in theexhaust line, a combustion chamber in the case upstream of the catalystmaterial, an ignition spark plug in the exhaust line upstream of thecombustion chamber, and means for supplying fresh air to the exhaustline upstream of the spark plug, the air supply source providingsuflicient air at high engine speeds with proper regulation at lowengine speeds, and at a rate which is not proportional to the enginespeed.

Some of the factors which must be considered in connection with this airsupply source for supplying fresh air to the exhaust [line upstream ofthe spark plug} system at a point where the air will improve oxidationof the exhaust ingredients are as follows: [Using a 235 cubic inchdisplacement engine, such as a Chevrolet 6 cylinder engine, as anexample (proportionally more air being required for larger displacementengines), at engine idle speeds of about 450 rpm, my converter systemrequires between about 1 /2 and 2 cubic feet of air per minute. At thistime the amount of excess air which is added is a relatively largepercentage of the exhaust volume, which is on the order of 6 cubic feetper minute.

However, when the automobile is in high speed operation, such as on afreeway, the hydrocarbon and carbon monoxide content of the exhaust gasis low, so that the excess air added to the exhaust need be only a verysmall percentage of the exhaust volume to perform its function ofburning these small percentage components. In most cases, with theengine in properly regulated condition, an amount equal to about 2 cubicfeet per minute is sufiicient. At this time the volume of exhaust gasesmay exceed cubic feet per minute. If quantities of air in excess of thisamount are added, then the excess air serves no beneficial function ofconversion, but does have the detrimental efiect of cooling thecatalytic converter.

At the time of high speed operation the exhaust gases, undiluted withcold air, will reach 1200 F. to 1300" F. temperature, and with about 2cubic feet per minute of air will be quenched to about 11SO F. If largeramounts of air are added, the converter temperature will beproportionally reduced. At the time of this type of high speedoperation, it is not important that the temperature be abnormally highbecause hydrocarbon and carbon monoxide contents are approachingspecification quantities anyway. However, if at such time air is addedto the exhaust stream to give a temperature of about 850 F. to 900 F.,then when deceleration, idle or heavy acceleration follows, andhydrocarbon and carbon monoxide quantities are both of high level, thecatalyst temperature (particularly if the converter has been used on theroad for an extended period) would be too low to spontaneously ignitethe carbon monoxide (which is, by far, the

highest source of burning heat). Since the exhaust gases underdeceleration or idle are at a temperature of about 400 F., the catalystbed without the benefit of the burning carbon monoxide would thenrapidly cool and the exhaust gases would not be properly treated] Thereare four principal modes of automotive operation, and in standardtesting procedures such as those prescribed by the State of CaliforniaAir Pollution Control Board the hydrocarbon and carbon monoxideemissions are measured for each of these four modes of operation. Thesefour modes of vehicle operation are idle, acceleration, deceleration andcruise. In determining the efiiciency of any anti-smog system that isbeing tested, the results of these tests for the four difierent modesare weighted according to the percentage of the vehicle operation whichis attributable to each of the modes.

T he percentage of air which must be introduced into the exhaust systemin relation to the exhaust volume varies widely for these four difierentmodes of operation. Thus, during the idle mode of operation, therequired amount of added air is a relatively large percentage inrelation to the exhaust volume. This is generally the result of a richmixture at idle and a substantially closed throttle valve which admitsonly a small amount of air through the carburetor.

In the acceleration mode, for substantially complete oxidation of theunoxidized and partially oxidized exhaust ingredients only a smallpercentage of air need be added in relation to the exhaust volume. Thisis in part the result of the fact that the throttle valve is relativelywide open during acceleration, thus admitting a relatively large amountof air through the carburetor, a portion of which is not consumed in thecylinders and passes on to the exhaust system.

During deceleration from highway speeds there is the greatest need foradded air in relation to the exhaust volume. This is in part caused bythe fact that the engine is turning relatively rapidly, but is beingstarved for air because the throttle valve is substantially closed, sothat combustion in the cylinders is relatively inefiicient andsubstantial quantities of unburned and only partially burned fuel aredumped into the exhaust system fromthe engine.

During cruise, generally at highway speeds, the need for added air as apercentage of exhaust volume is intermediate between the need duringacceleration and deceleration.

The slip-clutch drive from the engine to the air pump in the combinationof the present invention operates to automatically adjust the percentageof air furnished by the pump in relation to the exhaust volume.Generally speaking, the volume of exhaust flow will follow engine speed,increasing or decreasing according to an increase or decrease in enginespeed, and if the air pump were driven from the engine without theslip-clutch drive of the present invention the percentage of air inrelation to the exhaust volume would be generally constant regardless ofwhich of the four modes of operation is occurring. However, theslip-clutch drive between the engine and the air pump is sensitive tothe air pump output load, which is determined by back pressure in theexhaust system. Thus, if the back pressure is relatively low in theexhaust system, the air pump runs under a relatively light loading andthere is little or no slippage in the slip-clutch drive; on the otherhand, when the back pressure in the exhaust system is relatively high,there is a relatively high output loading on the air pump, which in turncases a relatively large amount of slippage in the slip-clutch. The backpressure condition of the exhaust system varies widely for the fourimportant modes of vehicle operation referred to hereinabove, and theamount of back pressure for each of these four modes of operationcorrelates approximately with the amount of slippage in the air pumpslip-clutch that is required to provide approximately the requiredamount of air for that mode.

Thus, for the idle mode, where a relatively large percentage of air isrequired in relation to the exhaust volume, there is a condition of verylow back pressure in the exhaust system, so that there is little or noslippage in the slip-clutch, and a relatively large percentage of airwill be furnished in relation to the exhaust volume as required.

Conversely, during the acceleration mode, when there is a relativelysmall demand for added air, the exhaust system is under its highest backpressure, which causes the greatest loading on the air pump output andthus the greatest amount of slippage in the slip-clutch. Consequently,the amount of air introduced into the exhaust system from the air pumpis relatively low in relation to the exhaust volume.

During deceleration from highway speeds, there is a large demand foradded air, and this is accommodated because of the fact that during thismode of operation there is a minimum amount of back pressure in theexhaust system, with a consequent minimum of slip-clutch slippage and arelatively large production of air in relation to the exhaust volume.

During the cruise mode, the exhaust system is in a condition ofintermediate back pressure between the back pressures found in theacceleration and deceleration modes, and thus there is an intermediateamount of slippage in the slip-clutch drive, and an intermediate amountof air provided by the pump in relation to the exhaust volume.

Accordingly, there is a new cooperation between the engine, exhaustsystem, air pump and slip-clutch drive between the engine and the airpump for automatically providing approximately the required amount ofadded air to the exhaust system for substantially completely oxidizingexhaust ingredients which were previously either unoxidized or onlypartially oxidized.

It is another object of the present invention to provide a novelapparatus and method of the character described for reducing theunburned hydrocarbon and carbon monoxide content of the exhaust gasesfrom an internal combustion engine, wherein a. spark plug of novelconstruction is employed to obtain cflicient pro-ignition of the carbonmonoxide and hydrocarbons in the exhaust gases before the gases cuterthe catalyst bed, without likelihood of blowout of the plug even underoperating conditions in which the velocity of the exhaust gases past theplug is extremely high, the spark plug including "a ringshaped outerelectrode suspended from the threaded mounting sleeve of the plug, and.a center electrode membcr extending centrally into the ring-shapedouter elcctrodc, whereby ignition between the electrodes is shieldedfrom blowout by the ring-shaped outer electrode.

This outer electrode ring, being rather heavy, also appears to maintaina degree of heat beneficial to ignition. For example, the ring duringhigh-speed operation will gradually increase in tcmpcrature to thetemperature of the exhaust stream of gas; namely, 1200 F. to 1300 F., aglowing condition. Immediately following a highspccd operation, it isnormal that a period of rather sudden deceleration will take place andlarge excesses of hydrocarbon will be contained in the exhaust stream.Aside from the benefit of the spark per se, it appears that the heavymetal ring (not having sufficient time vto cool below a glowing heat)will also initially ignite the exhaust mixturc, and since the flame dueto exhaust velocity is swept away, downstream of the spark plug, thespark then continues the fia-mc ignition until a non-combustioncondition (lower hydrocarbon and carbon monoxide mixture) eventually iseffective, and the burning goes out.

It is a (further object of this invention to provide an apparatus andmethod of the character described wherein a particulate catalyst iscontained in :a catalytic case which replaces the conventional exhaustmufi'lcr, the case having a forward combustion zone and a catalyst zoncbehind the combustion zone, the catalyst zone being separated from thecombustion zone at the upstream end of the catalyst zone by a conicallyshaped screen which points forwardly or upstream, and the rear end ofthe catalyst zone being defined by a similar conically shaped, forwardlydirected screen, whereby a small exposed quantity of catalyst materialin the tip of the front cone will heat up quickly to give a suddenkickoff to the catalyst reaction immediately after the engine isstarted, even when the exhaust system is cold; while at the same timethe complementary conical shapes of the catalyst zone end walls are suchthat the catalyst bed has an equal depth from front to rear at allpoints :across the catalyst bed. Also, the iorward cone, due to itsshape and the "elocity of the exhaust gases impinging upon the apex ofthe cone, causes high turbulence of the air-exhaust mixture entering thecase and provides better mixing and burning before entering the catalystbed section, thereby more completely oxidizing the components.

The tip of the forward cone is subjected to very high temperatures inwhat appears to be an oxidizing environmcnt, and therefore has atendency to burn after prolonged road operation of the converter. Thisburning or eating away of the tip of the forward cone may rcsult fromnascent bromine released from the burning of tctraethyl lead which isassociated with the bromide, rather than from oxygen as such. In orderto protect the tip of the forward cone from such deterioration, it ispreferable to support a protective disc or button composed of a materialwhich will not be damaged under the heat and atmosphere conditionspresent in the case in the combustion zone of the catalytic case justforward of the cone apex, and centrally located. This protective disc orbutton not only protects the tip of the forward cone by diverting theaxial flow of hot gases at that time, but also serves to deflect thefinely divided lead Eoxidj; oxide formed in the exhaust burningsponsored by the spark plug, throwing it out to the edges of thecombustion chamber where it is deposited against the inner wall of thecase, thus preventing the lead oxide from blinding the catalyticparticles and smothering their catalytic action. The lead oxide ispossibly augmented by some road silt which was too fine for the airfilter system to remove. This deposited material tends to be tacky, sothat some of it will adhere to the ceramic button, while the remainderwill be deflected and accumulated in the inner wall of the case. Byproviding a concave forward face on the button, the deflection will beenhanced, and a recess will be provided to hold a substantial amount ofthe accumulated material.

The protective button may be made out of ceramic slip containing activecatalyst impregnation materials as a part of the slip formula. In thisway, the rather violent impingement of the abnormally hot gases and airmixture upon the catalytic ceramic disc will tend to set off the burningof the carbon monoxide at this point, and generate quick, high gradeheat almost immediately upon starting the car, lowering the catalyticrequirements of the catalyst bed following it.

Another object is to provide, in apparatus of the character described, acatalyst material comprising a solid base material having a porous,clay-like surface, with a thin surface impregnation of catalyticallyactive material on the base, the preferred depth of the catalyticimpregnation being of the order of about 0.10 inch, and within apreferred range of from about 0.005 inch to about 0.020 inch, wherebysubstantially all of the active catalytic material is employed in thereaction, and whereby the catalyst structure, including both base andactive catalytic materials, has a minimum thermal conductivity and heatcapacity so that the catalyst bed will heat up as quickly as possibleand will retain its heat as long as possible, in order to provideoptimum catalytic action. As a part of the present invention, I providea novel method for applying this thin impregnation of the activecatalytic material on the inert base which involves the application ofhot, super-saturated impregnation solutions to the cold base material,whereby the impregnation solutions will freeze or solidify in a thineggshell surface of impregnation which is controllable by the degree ofsuper-saturation and the temperature range employed.

It is also an object to provide a novel combination of active catalyticmaterials, preferably comprising iron oxide, copper oxide and chromicoxide, the copper oxide being effective to commence the catalytic actionat relatively low starting temperatures, and the iron oxide and chromicoxide providing eificient higher temperature operation.

My new catalyst composition, and also the thin surface applicationthereof, may be embodied either on particles of the base material havinga mean diameter preferably on the order of about .17 inch and in apreferred range of from about .15 inch to about .24 inch; or may beembodied in a porous ceramic block of the base material. The basematerial preferably has a porous, clay-like surface, and if the basematerial is of a glassy or silicious nature, then this material may besurfaced with a very thin layer of clay-like material prior to or inconjunction with the application of the oxides performing the catalyticfunction.

The porous ceramic catalyst blocks may be formed with internal wallswhich separate the passages therethrough having a thickness on the orderof 0.020 inch or less, so that when these walls are substantiallycompletely impregnated with the active catalytic material, the entireuseful depth of about .010 inch or less on both sides of the walls wouldbe employed, thus giving a maximum possible efiiciency for a givenvolume of the catalyst, with a low heat capacity and conductivity and agreatly extended surface (per given volume) for contact with the exhaustgases.

In the instance of using the ceramic bricks as the catalytic members inthe case, it is preferable to include the relatively non-porousprotective ceramic disc or button in the combustion chamber ahead of thebrick. As with the particulate catalyst, the ceramic button will divertmuch of the particulate lead oxide to the wall of the case in thecombustion zone ahead of the brick so as to protect the catalyticsurfaces of the brick.

EA further object of the invention is to provide, in apparatus of thecharacter described, an air pump or compressor for providing freshcombustion air to the exhaust line substantially upstream of the sparkplug and catalyst case, the air compressor embodying a novel slipclutchdrive so that the compressor may be driven off of the engine, as byconnection with the fan belt, with a minimum of slippage at low enginespeeds, and considerable slippage at relatively high engine speeds, toget the desired air-exhaust proportion over all engine speed ranges.

In addition to the slip-clutch drive for regulating the compressoroutput, it is also desirable to provide a mechanical regulator to limitthe output of the compressor. Such a mechanical regulator may simplycomprise a bypass conduit from the compressor outlet port to the inletport, with a normally closed pressure responsive relief valve in thisconduit adapted to open so as to bypass excess air output of the pumpwhen the back pressure on the outlet port exceeds a predeterminedminimum value} Further objects and advantages of the present inventionwill appear during the course of the following part of the specificationwherein the details of construction, mode of operation and novel methodsteps of a preferred embodiment are described with reference to theaccompanying drawings, in which:

FIGURE 1 is an elevational view showing an internal combustion enginehaving an exhaust system embodying the present invention.

FIGURE 2 is a vertical section showing a form of diffuser which may beemployed in the exhaust line upstream of the catalytic case and sparkplug to give the desired turbulence for mixing injected air with theexhaust gases where the exhaust pipe itself does not have the equivalentof two right-angle bends to provide such turbulence.

FIGURE 3 is a horizontal section along the line 3-3 in FIGURE 1illustrating a presently prefer-red embodiment of my catalytic case forcontaining my particular type of catalyst.

FIGURE 4 is a vertical section along the line 4-4 in FIGURE 3 furtherillustrating the catalytic case, and showing my preferred spark plug.

FIGURE 5 is a cross-sectional vie along the line 5-5 in FIGURE 4 furtherillustrating the preferred catalytic case.

FIGURE 6 is an elevational view similar to FIGURE 1, but illustrating analternative air injection system wherein the air line is formed in aheating coil in the rear end of the catalytic case, and then extendsupstream to the catalytic case and through a substantial part of theexhaust pipe to introduce the air in the exhaust pipe near the engine.

FIGURE 7 is a vertical section similar to the left-hand part of FIGURE 4but enlarged to further illustrate the details of construction of thefront part of the catalytic case and of the spark plug and the plugmounting.

FIGURE 8 is a perspective view of my new spark plug.

FIGURE 9 is an elevational view partly in section, further illustratingthe details of construction of the spark plug.

FIGURE 10 is a horizontal section along the line 1010 in FIGURE 9.

FIGURE 11 is an axial, vertical section illustrating a modified form ofcatalytic case embodying a plurality of my porous, ceramic catalystblocks.

FIGURE 12 is a cross-sectional view along the line 1212 of FIGURE 11.

FIGURE 13 is a perspective View of one of the individual ceramic blocksshown in FIGURE 11.

FIGURE 14 is an axial, vertical section illustrating an alternativeceramic catalyst block construction wherein the forwardmost block has aforwardly projecting conical portion, and the rearwardmost block has acomplementary conical recess.

FIGURE 15 is a side elevation view of an air pump having a slip-clutchdrive which I have found to be suitable for providing combustion air tothe exhaust line in practising my present invention.

FIGURE 16 is an end elevation view of the pump shown in FIGURE 15,looking from left to right in FIGURE 15.

FIGURE 17 is an end elevation view of the air pump looking from right toleft in FIGURE 15.

FIGURE 18 is an axial vertical section showing the internal details ofconstruction of the pump in FIGURE FIGURE 19 is a cross-sectional viewalong the line 1919 in FIGURE 18 showing further details of the pump.

FIGURE 20 is a cross-sectional view taken on the line 2020 of FIGURE 18showing details of the slip-clutch assembly.

FIGURE 21 is a sectional view along the line 21-21 in FIGURE 20 showingfurther details of the slip-clutch construction.

FIGURE 22 is a fragmentary cross-sectional view along the line 22-22 inFIGURE 18 illustrating a [presently preferred} mechanical outputregulator {forming} which may be employed as a part of the pump.

Referring to the drawings, in FIGURE 1 I have illustrated a conventionalinternal combustion engine 10 having exhaust manifold 12 and exhaustpipe 14 attached thereto. Exhaust pipes currently employed have aninternal diameter on the order of about 2 inches.

An air pump 16, preferably of the positive displacement type, providesair to the exhaust pipe 14 near its connection to manifold 12 through asuitable conduit 18. I have found that a copper tube having an internaldiameter of inch is adequate for the conduit 18. I prefer to include acheck valve 20 in the conduit 18 to protect pump 16 from exhaust gasesin the event of pump failure. If desired, the check valve may beprovided immediately adjacent to or as a part of the air pump 16, andmay comprise a diaphram of neoprene or flexible plastic with a valvebase or seat upstream of the diaphram comprising a part of the pumpdischarge port. The downstream side of this diaphram is connected to airconduit 18 at a properly shaped fitting which is easily removable forreplacing or inspecting conduit 18.

If desired, conduit 18 may be partly of plastic hose from the air pumpto a point closely approaching the entrance to exhaust pipe 14, withmetal forming the portion of conduit 18 immediately adjacent to theexhaust pipe. With this construction, in case of failure of the checkvalve 20, the plastic hose will melt and discharge any hot exhaustgases, thereby protecting both the compressor and the check valve.

[Although the pump 16 may be driven by any desired means, such as by asmall electric motor,] I have found that [it is] the most practical wayto actuate the pump is to drive the pump directly off of the engine fanbelt 22. Pump 16 may be driven off of either the inside or the outsideof the fan belt, and may conveniently be mounted on the vehiclegenerator if desired.

Because the EThe] air requirements of my present invention are notnearly proportionate to engine speed, and because of the widely varyingrequirements for air in relation to the exhaust volume for the fourprincipal modes of vehicle operation, idle, acceleration, decelerationand cruise, it is [accordingly] desirable to provide a variable drivefor the pump 16. [Thus, for engine idle speeds of about 450 rpm, myconoverter system requires between about 1 /2 and 2 cubic feet of airper minute, while at highway speeds on the order of 65 miles per hour,when the engine is rotating at about 2500 r.p.m., the air requirement isonly about 2 cubic feet per minute, these figures being for a 235 cubicinch displacement engine (such as a Chevrolet 6 cylinder engine), withlarger displacement engines requiring proportionally more air. Althoughdifferent types of variable drives may be employed to achieve thedesired speed ratio between the engine and the pump, such as acentrifugally slipping clutch arrangement or a variable belt drive,] Ihave found in practice that a slip-clutch drive construction like thatshown in detail in FIGURES 1522 is particularly suitable for the presentpurposes. This drive has the desirable characteristic of beingresponsive to back pressure in the exhaust system, whereby underrelatively low back pressure the drive coupling operates the air pumpfor delivery of a relatively large percentage of air in relation to theexhaust volume and under relatively high back pressure the drivecoupling operates the pump for delivery of a relatively small percentageof air in relation to the exhaust volume. This results in theintroduciton into the exhaust system of approximately the requiredamount of added vair for substantially complete oxidation of exhaustingredients under the various modes of vehicle operation, therebypromoting maximum combustion in the exhaust system. Except for thedeceleration mode of vehicle operation, there will normally be greatlyincreased slippage with increases in engine speed because of theincreased back pressure from the higher exhaust volume, therebymaintaining only a small increase in pump air output at high cruisingspeeds over that at low speeds. Also, this slip-clutch drive, bypermitting only a relatively small amount of increase in the pump speedfor high engine speeds during cruising as compared With the pump speedfor low engine speeds, keeps the pump operating within a speed rangewhich will involve a minimum of Wear and tear in the pump, and willactually prevent rotor blade breakage, pump speeds above 4000 rpm.usually destroying or causing rapid erosion of the carbon blades.

Also, it has been found in actual road operation that if the pump has aburned-out bearing or broken blade, the slip-clutch will continue to runand the belt and pulley will function normally; where otherwisesomething else must giveway, which would result in a burned-out belt orfurther damage to the pump.

As a further means for controlling the pump output volume so as to limit[it to the desired 2 cubic feet per minute (for an engine having adisplacement of approximately 235 cubic inches, this figure varying forengines having different displacements),] its output to a fixed valueunder conditions of maximum back pressure (which may occur duringacceleration or at high vehicle speeds) [I prefer to employ]pressure-responsive mechanical regulating means may be associated withthe pump outlet for diverting excess air output of the pump. An exampleof a suitable regulating device for this purpose is describedhereinafter in connection with FIGURE 22 of the drawmgs.

The air is introduced into exhaust pipe 14 near the manifold 12 to getthe best possible mixing of the air with the exhaust gases. I have foundin practice that to achieve the desired mixing of the air with theexhaust gases for optimum results, it is preferable to have theair-exhaust mixture pass through the equivalent of at least tworightangle bends in the exhaust line before the mixture is fired. Inmany cases, the exhaust pipe will already have a configuration whichincludes the equivalent of two right-angle bends, as, for example, theright-angle bends 24 and 26 in the exhaust pipe 14 shown in FIGURE 1.However,

if the exhaust line on a particular vehicle does not include theequivalent of two right-angle bends, a diffuser may be placed in theexhaust line upstream of my spark plug and catalytic case to achievesimilar results. Such a diffuser is shown in FIGURE 2, and may merelycomprise a small housing 36 disposed in the exhaust line 14, with atransverse bafile plate 32 in housing 30 to divert the flow of exhaustgases and air.

It is desirable to provide a heat-insulating covering over the exhaustpipe 14 between the inlet from air conduit 13 and the spark plug so asto retain the air-exhaust mixture at the highest possible temperaturefor firing. This insulation may be composed of asbestos or othersuitable insulating material.

My catalytic case 34 replaces the conventional muffler in the exhaustline, and has external dimensions comparable to those of theconventional muffler to conform with chassis and road clearancelimitations. My spark plug 36 is mounted in the exhaust line closelyadjacent to the catalytic case 34 on the upstream side of case 34. Forconvenience in mounting plug 36, I prefer to provide a special sleeve 38which is connected at its upstream end to exhaust pipe 14 and itsdownstream end to the catalytic case 34. Sleeve 38 is provided with athreaded opening to receive the plug 36.

I have found that a conventional spark plug will blow itself out underhigh exhaust flow conditions, and that a conventional plug will not fireat low exhaust temperatures. To overcome these objections, I haveprovided my new spark plug 36, which is best shown in detail in FIGS. 7,8, 9 and 10.

Plug 36 includes the usual externally threaded mounting collar 42.Integrally attached to and extending from the lower edge of collar 42are a plurality of support rods 44. Preferably two of these rods 44 areemployed, being joined to the bottom edge of collar 42 in diametricallyopposed relationship. Support rods 44 may be peaned into holes providedin collar 42, or may be otherwise connected to collar 42, as by welding.

The outer plug terminal 46 comprises a short sleeve member mounted onthe lower ends of support rods 44 in axial alignment with the plug. Thelower ends of support rods 44 may, if desired, be peaned intodiametrically opposed holes in the upper edge of the outer terminal 46,or attachment may be made by other means, such as welding or the like.

The inner plug terminal 48 projects downwardly from the center of theplug and has its lower end axially positioned within the outer terminalsleeve 46.

I prefer to suspend the outer terminal sleeve 46 approximately one inchbelow the plug mounting collar 42, thus to place the outer terminalsleeve 46 at substantially the axial center of the exhaust line, whichhas an inner diameter of approximately 2 inches. This positioning of theplug terminals in the axial center of the exhaust flow gives the bestpossible firing results.

Although the terminals of my plug 36 are not limited to any particularsizes, I have achieved excellent results with a plug of this type havingan outer terminal sleeve 46 that is about one-quarter inch deep, havinga wall thickness of about inch, and having an inner cylindrical wallspaced about 64 thousandths of an inch from the inner terminal 48.

My new spark plug 36 has proven extremely effective in use withoutfailure or fouling, and will not undergo blowout under any conditions ofautomobile operation. The spark will be ignited between the outerterminal 46 and the inner terminal 48 regardless of the amount ofvelocity and turbulence of the exhaust gases as they pass the plug.Ignition of the exhaust gases by the plug has been observed for exhaustgas temperatures as low at 300 F., which permits my present device toeifectively burn unwanted hydrocarbons and carbon monoxide within amatter of seconds after a cold start. For example, when a coldautomobile is started, and the exhaust gases are low in temperature, ifthe automobile operates at a speed even as low as 20 miles per hour, anddecelerates within the first minute of operation, the spark plug hasbeenfound capable of firing the air exhaust mixture thus produced suddenly,and thereby to raise the temperature to as high as W E, thus quicklyheating the catalyst and preventing catalyst lead poisoning whichotherwise is particularly bad at such times because the catalyst bed isstill cold and overly adsorptive.

The presently preferred catalytic case 34 is illustrated in FIGS. 1, 3,4, 5 and 7 of the drawings. The catalytic case 34 of my preferredconstruction includes cylindrical outer and inner metal shells 5i and52, respectively, with an insulation layer 54 between shells 5'0 and 52.Any desired insulation material may be employed in layer 54, as, forexample, glass wool, woven kaowool, asbestos or the like. The outer andinner shells 5i and 52 may be rolled together with a sheet of theinsulation material between them to form the cylindrical portion of thecase. For economy and durability, I prefer to employ mild steel for theshells 5t) and 52, and it is best that the steel be aluminized toprevent rust and corrosion. Stainless steel could also be used, butwould be more expensive.

I employ the double-shell, insulated case because of the fact thatburning or both hydrocarbons and carbon monoxide in my device causestemperatures as high as 1790 F. to be produced in the case at times, andthe double insulated case protects underside equipment of theautomobile, such as brakes, from damage which might otherwise occur fromsuch temperatures, and also protects against car-occupant discomfort.This insulated case also protects against splashing of road water, snowand the like upon an abnormally hot outer surface.

The double wall of the case is approximately onequarter of an inchthick, and it is preferable to have a flat, oval shape for thecylindrical case as best shown in FIG. 5 so as to minimize flat surfacesor sides which under internal pressure would tend to bulge and enlargethe internal volume of the catalyst case. In order to provide adequatevolume for the catalyst bed and forward combustion chamber, I prefer toemploy a cylindrical case having internal dimensions of approximately 5inches high by 12 inches wide by about 24 inches long.

The forward and rear heads 56 and 58 of the case are, like thecylindrical portion of the case, preferably of a double-walled insulatedconstruction, and are pro vided with peripheral flanges 69 so that theends of the outer metal shell 50 may be crimped around flanges iii) tosecure the -forward and rear heads 56 and 58 in position.

The heads 56 and 58 are provided with proper openings defined withinaxial connection flanges 6-2 and 64, respectively. Thus, the plugmounting sleeve 38 is integrally attached within the connection flange62 of forward head 56 as by welding, while a rear portion 66 of theexhaust pipe which opens to the atmosphere is integrally connectedwithin the connection flange 64 of rear head 58, as by welding.

It has been found in practice that the catalyst bed itself should havean axial depth at least twice its mean cross-sectional diameter, and inmy presently preferred catalyst case I employ a catalyst bed depth ofabout 14 /2 inches. The catalyst bed 68 is contained in the inner metalshell 52 of the case between axially spaced front and rear conicalscreens 76 and 72, respectively. The front and rear screens 70 and 72,respectively, point forwardly, or upstream, and are of identical shapeso that the axial depth of the catalyst bed is uniform across the bed.For a catalyst case of the preferred dimensions set forth above, Iprefer to employ conical screens 70 and 72 which have an axial depth ofabout 3 inches from the base 74 to the point 76 of each screen. Thebases 74 of screens 74? and 72 are positioned directly against the innerwall of inner metal shell 52. I

The conical screens 79 and '72 are preferably composed of a stainlesssteel screen having a mesh on the order of between about 15 to wires tothe inch. Such screen material has adequate strength and serviceability,and still is fine enough so that the relatively large catalyst particleswill not blind the screen from the rapid passage of the exhaust gasestherethrough.

The conical screens 70 and 72 do not have sufficient structural strengthto support themselves, and are accordingly backed-up by respectiveperforated conical plates 78 and 80 to which screens 72 and 74 arespot-welded. The conical plates 78 and 80 are integrally secured to theinner metal shell 52, as by welding. The catalyst particles are actuallycontained by the screens 70 and 72 so that the particles can not blindthe perforations in the conical plates 78 and 83. Thus, the frontconical screen 70 is secured to the rear or downstream side of the frontperforated plate 78, while the rear screen 72 is secured to the forwardor upstream side of the rear plate 80. I have found in practice that arear perforated plate 80 composed of mild steel holds up very well, butthat it is preferable to provide front perforated plate 78 of stainlesssteel, or possibly aluminized steel, because of the blasts of fire inthe ignited exhaust from the spark plug, which not only causes hightemperatures but also causes the front perforated plate 78 to go throughvery sudden shock temperature changes and stresses.

It will be noted that the front conical plate 30 is disposedconsiderably downstream or to the rear of the forward head 56 of thecase, thus providing a combustion chamber 82 in the case forward of thecatalyst bed. The distance between the base of the front plate 80 andthe inside of the forward head 56 is about 8 inches in my preferredcatalytic case 34 as described herein. This relatively large combustionchamber 82 directly' ahead of the catalyst bed within the case 34 is animportant component of my invention, providing space to burnconsiderable quantities of hydrocarbons and carbon monoxide which havebeen ignited by the spark plug 36 before the exhaust gases enter thecatalyst bed. Expansion of the gases from the plug mounting sleeve 38into combustion chamber 82, and the intrusion into the combustionchamber 82 by the forwardly pointing conical plate 78 and screen 70cause a great deal of gas turbulence in chamber 82 to promotecombustion. I have found that by placing the spark plug 36 in theexhaust line just ahead of chamber 82 rather than in chamber 82, theplug is more intimately associated with the gases, due to the narrowchannel through which the gases pass, to provide the most effectiveignition.

Combustion in the chamber 82 serves three important purposes. First, itgenerates heat to raise the tempera ture of the catalyst bed morequickly and to a higher temperature, so as to achieve the best possiblecatalyst action in the bed. Second, it accomplishes part of the burningof hydrocarbons and carbon monoxide, thus removing excessive reactionrequirements from the catalyst bed itself. Third, the combustion of theexcess hydrocarbons ahead of the catalyst bed protects the catalyst to amajor degree from lead poisoning, this being particu larly importantwhen a considerable quantity of raw gasoline passes through the exhaustsystem, as during sudden automobile deceleration. A sudden release ofthe accelerator pedal creates a high vacuum on the carburetor, causingexcess gasoline to pass through the engine with substantially incompletecombustion, causing the exhaust gases to be high in unburned or onlypartially burned gasoline. The tetraethyl lead in this gasoline is in anorganic form and when adsorbed by a catalyst, impregnates the catalystwith a soluble lead compound, thus poisoning the catalyst. However, withmy preignition of this deceleration gasoline-air-exhaust mixture, thelead-organic compounds are burned and substantially destroyed beforeentering the catalyst bed, the lead content of the exhaust whichactually enters the catalyst bed being in the form of lead oxide dustwhich will either pass through the catalytic bed unadsorbed, or willmerely coat the catalyst particles as a light powder which willultimately blow out of the catalyst bed as it accumulates.

One of the principal advantages of employing the conical catalystretainer screens is that a small volume of the catalyst in the apex ofthe front cone is, in effect, exposed to the heat of the ignited gasesin combustion chamber 82 so that it is quickly heated to the 500 or moredegrees F. required for effective catalytic action, thus kicking.- offthe catalyst reaction in the catalyst bed 68. By this means, effectivecatalyst action occurs within about the first minute after a cold engineis started.

To protect the apex portion of the front cone from high temperatureoxidation which might otherwise occur as a result of the directimpingement of the high temperature exhaust flow against the cone apex,and further to provide a means for diverting the lead oxide dust" andfine road silt which may be contained in the exhaust stream toward theinner wall of the case so that these finely divided particles will notblind the catalyst bed, I prefer to support a heat resistant protectivedisc or button 71 just forward of the cone apex in a central positionwithin the case. The disc or button 71 may be composed of any suitableheat and chemical resistant material. An example of a suitable materialis relatively nonporous ceramic, quartz or the like, which has lowcoefficient of thermal expansion or contraction. Control over thethermal expansion or contraction in the ceramic may be achieved byincluding appropriate quantities of lithium in the ceramic composition.The protective button may, if desired, be composed of a metal or anyother material which will withstand the temperature and chemicalconditions present in the case. An example of a suitable metal isnichrome. Although this protective button is not critical as to size, ina catalytic case having the preferred dimensions as set forth above, thebutton is preferably about 2% inches in diameter, with an axialthickness of about %1 inch. In order to enhance the deflection of thelead oxide particles so that a maximum thereof will be deposited on theinner wall of the case, and also to provide a receptacle for retaining asubstantial quantity of the relatively tacky deposited material on thebutton itself, I prefer to provide a concave forward face 73 on thebutton 71. The axial depth of the concavity of face 73 is preferablyabout /2 inch for a button 71 which is about inch thick.

The button 71 is preferably made out of ceramic slip like that used inmaking ceramic catalytic blocks as hereinafter described in connectionwith FIGS. 11, 12, 13 and 14 of the drawings, but with the ceramicbutton being made in a relatively nonporous form. It .is desirable toinclude as a part of this slip formula impregnation materials such asthose hereinafter described in connection with the particulate andporous ceramic catalyst-s for providing active catalytic chemicals inthe ceramic button. By thus including the active catalytic agents in theceramic button, the rather violent impingement of the hot gases and airmixture of the exhaust stream upon the ceramic button will tend to setoff the burning of the carbon monoxide at this point, quickly generatinga considerable amount of heat almost immediately upon starting the car,thereby lowering the catalytic requirements of the catalyst bedfollowing the button.

The protective disc or button 71 is preferably positioned relativelyclose to the forward cone apex, on the order of about A; inch forward ofthe cone apex in the catalytic case of the aforesaid preferreddimensions. Although the button may be supported in this position in anyconvenient manner, a presently preferred means is to provide a pair ofmetal rods 75 and 77, which may be of welding rod stock, if desired, therods extending at right angles to each other through a pair of diametralholes through the disc, with the ends of rods 75 and 77 being welded tothe inner wall of the case.

With further reference to the preferred catalytic case 34, it is easierto introduce the particulate catalyst into the case after the case hasbeen completely constructed, and it is therefore desirable to provide anopening 84 through the case wall, which may merely be punched out, theopening 84 communicating with the inside of the case just forward of therear screen 72. After the catalyst has been loaded, the opening 84 maybe covered by a suitable cap 86. Cap 86 may be attached to the case byinserting a bar 87 across the inside of opening 84, with a screw 88extending through cap 86 and threadedly engaged to bar 87.

A plurality of axially spaced ribs 90- extend inwardly of the inner caseshell 52 into the catalyst bed 68. These ribs 90 extend all of the wayaround the inner shell 52. The portions of ribs 96 which extend acrossthe top wall of shell 52 are preferably about inch wide so as to servenot only as case stiffener-s but also to serve as baffles to preventchanneling of the gases through the catalyst bed in the event of anycatalyst shrinkage. The remaining portions of ribs 90 at the sides andbottom of shell 52 may only be about inch wide, serving primarily tostiffen the case against deformation.

Referring now to the catalyst itself, the minimum size of the catalystparticles is governed by the maximum acceptable back pressure on theexhaust. However, the smaller the catalyst particles, the greater theamount of effective catalyst surface area on the particles. I have foundin practice that a mean particle diameter of about 0.17 inch issatisfactory, and that the particle size ranges preferably between about0.15 inch and about 0.24 inch will achieve satisfactory results.

The catalyst particles comprise a carrier base which has a porous,clay-like, unglazed surface to permit impregnation by the activecatalytic material. Since the catalyst must be capable of resistingsudden temperature changes, on the order of 100 F. to 1900 F. in amatter of seconds, the catalyst base should be one which does not heatfracture or shrink during use, which might cause voids where gases mayby-pass without catalytic contact. Another important characteristic ofthe catalyst is that it should have a low heat capacity, so that thecatalytic bed will heat quickly from a cold start. Also, the catalystshould be a poor heat conductor, so that it will not dissipate the heatof reaction too quickly and will remain at a higher effectivetemperature during operation. Such low heat capacity and conductivitymay be provided by use of a base material of as low density as possible,and by adding to the base particles only that amount of active catalyticmaterial which is actually usable during the catalytic reaction.

Although any base particles having the foregoing general characteristicsmay be employed, I have found base particles to be satisfactory whichare made of the mineral Kaolin as processed by Minerals and Chemicals,and commercially available in spheres called Kaospberes, this materialbeing practically pure kaolin (45% A1 55% SiO However, this materialwill shrink when subjected to the temperatures present in my catalyticcase, and I therefore preshrink the particles before use at atemperature of 1900 F. to 2000 R, either before or after impregnation bythe active catalytic material.

It appears that the best catalytic surface is a clay-like surface whichcontains pores on the order of about 20 Angstroms diameter (determinedby nitrogen adsorption) with a minimum total surface within the pores ofabout 80 square meters per gram. This extended pore Angstrom surface notonly promotes excellent catalytic action of the active catalyticmaterial impregnated thereon, but also appears to provide an effectivetrap for the lead and other catalyst poisons in the exhaust, with enoughsurface left over to do a good job catalytically after many hours ofuse.

.Such a pore Angstrom surface exists in the Kaospheres before they arecalcined for pre-shrinking at 1900 F. to 2000" F. but it is believedthat this calcining may somewhat damage this finely porous surface. Forthis reason I prefer .to provide base particles of another materialwhich will have the desired characteristics of low heat capacity andconductivity and resistance to heat shrinkages, heat fraction andattrition, and to coat such base particles with a thin layer ofmicronized Kaospheres or other clay material, either before or duringthe impregnation of the active catalytic chemicals. Suitable baseparticles are extruded pellets of Celite, as made by Johns Manville.Celite is diatomaceous earth which is pure silcon oxide, and particlesof this material do not appear to undergo any appreciable shrinkage attemperatures up to 2000 F., are very light in weight and are not likelyto undergo heat fracture, and after impregnation are relatively hard andnot likely to attrite through shaking on the road in the catalyst case.This coating of finely divided kaolin or other clay material on thesurfaces of the particles will not be calcined for shrinking, and hencewill have the desired large number of pores of the 20 Augstrom type.Because this coating is thin, if it does gradually shrin-k upon thesurface in use, this will not adversely [effect] affect the catalyst,since the base upon which it resides does not shrink, and therefore thecatalyst bed will still be of substantially constant size in the case.

Pellets of Cel-ite also appear to be effective as the base particleswithout this added clay-like coating where they are produced withcarbonaceous material which is burned out so as to leave pores in thepellets. A still further procedure for enhancing the catalyticperformance of the Cel'ite particles is to mix the Celite with kaolin orother clay material when the Celite pellets are extruded.

It will be apparent that a wide variety of base materials may besuperficially surfaced with a thin layer of clay-like material, even ifthe base is of a glassy or silicious nature or otherwise does notpossess the desired porosity. For example, base particles of pure silicaor pure almina may be employed when thus coated.

A wide selection of active catalytic chemicals is available forimpregnation of the carrier particles. However, oxides of themulti-valent metals are the presently preferred active catalytic agentsfor hydrocarbon and carbon monoxide oxidation because they maintain highactivity during use, they are relatively unsusceptible to poisons suchas lead, phosphoric acid, boron and sulfur, and because they arerelatively cheap. Oxides of such multivalent metals as iron, chromium,copper, cobalt, manganese, molybdenum, nickel, platinum and palladiumare etfective.

The usual prior art procedure for impregnating catalyst base particleswith such oxides is to soak the base in a solution of a salt of themetal (such as a nitrate or a sulfate), and then precipitate the metaloxide with ammonium hydroxide, and subsequently wash out the remainingsoluble salts (such as ammonium nitrate or sulfate) with water, and thenheat the catalyst to activate the catalyst, this heating sometimes beingperformed in a reducing atmosphere of hydrogen. This prior art soakingtreatment permeates the full depth of the base particles, and suchcomplete impregnation of the base particles with the catalyst is bothunnecessary and undesirable.

I have found that since the react-ion time of the catalyst particlesupon the exhaust gases is extremely short, being as low as one-tenth ofa second, the useful catalytic depth is only about 0.010 inch below thesurfaces of the particles. Any additional catalyst in the particlesbelow that depth appears to be completely wasted, thus unnecessarilyadding to the cost of the ingredients, and also considerably increasingthe density of the particles, thus undesirably increasing the heatcapacity and heat conductivity of the particles. Thus, in practicing thepresent invention, I limit the depth of the active catalytic 17chemicals to a preferred depth of about 0.010 inch, with a preferreddepth range of from about .005 inch to about .020 inch.

In order to thus limit the depth of impregnation, I apply asuper-saturated solution of the impregnating salts at elevatedtemperatures to cold base particles, which causes an instantaneousfreezing or solidifying of the impregnating solution on the surfaces ofthe particles, thereby preventing voluminous internal adsorption andcreating an eggshell surface of impregnation which can be controlled indepth by the degree of super-saturation employed and by the temperaturerange. Following this controlled surface impregnation, ammoniumhydroxide solution or ammonia gas is then applied for precipitating theoxide catalyst in this eggshell form, this being followed byconventional water washing. It is to be noted that in addition to theother advantages of this surface impregnation, the washing effectivenessis enhanced because of the availability of the salts at the surfaces ofthe particles.

I prefer to employ an active catalyst composition which includes ferricoxide which is promoted with a quantity of chromic oxide, and alsocopper oxide. I find that the copper oxide considerably aids the lowtemperature activity of the catalyst. A presently preferred impregnationsolution which is readily availia'ble and of relatively low costcomprises a 50% solution of ferric sulfate in water, which includes aquantity of chromic acid and some copper sulfate. This solution ispreferably heated to about 170 -F., although the temperature may bevaried according to the degree of super-saturation of the chemicalsolution. This solution is then applied to the base particles which areat ambient temperature, the chemical solution freezing as aforesaid toprovide the thin surface layer of impregnation. Ammonium hydrox idesolution or ammonia gas is then applied for precipitating the oxidecatalyst, and the particles are then water-washed. The Water-washingremoves the sulfate as water soluble ammonium sulfate, leaving the ironon the surface of the .base as iron hydroxide, which upon heating (at atemperature as low as 500 F.) evolves water vapor, reducing the ironhydroxide to iron oxide. This leaves a final catalyst impregnated agentcomprising a complex of ferric oxide, chromic oxide and copper oxide.

Although I prefer to include the chromic acid in the original ferricsulfate and copper sulfate solution, the chromic acid may,alternatively, be applied after the impregnation by the ferric sulfateand copper sulfate solution and the application of ammonium hydroxide orammonia to form ferric oxide and copper oxide, and after the particleshave been washed. This later application of the chromic acid may beaccomplished by tumbling or rolling the wet, water-washed particles witha quantity of dry flake chromic acid. The moisture on the surfaces ofthe water-washed catalyst particles dissolves the chromic acid, butsince the catalyst particles are already saturated with water, thechromic acid remains substantially on the surface with the iron oxideand copper oxide, and upon drying, is converted to chromic oxide. Theparticles are then heated for activation.

I prefer to use an impregnation formula which, after the final heatingor calcining leaves, per cubic foot of the catalyst particles, about 6lbs. of ferric oxide, 3 lbs. of chromic oxide and 1 /2 lbs. of copperoxide. Based upon weight percent of the base material, where the basematerial comprises Kaospheres, the preferred percentages of the activecatalytic ingredients are about 8% ferric oxide, 4% chromic oxide and 2%copper oxide. For the lighter density Celite 408 by Johns Manville,these percentages would be about 12% ferric oxide, 6% chromic oxide and3% copper oxide.

Referring again to FIG. 1 of the drawings, the spark plug 36 is providedwith interrupted, high voltage electricity from spark coil 9 throughelectrical conductor 94.

18 The spark coil 92 may comprise a conventional automobile spark coil,which is actually a high voltage step-up transformer. Interruptedcurrent is provided to the primary winding of coil 92 from theautomobile electrical system, this current being interrupted by a set ofinterrupter points 96 which, if desired, may be actuated by a cam memberconnected to the shaft of air pump 16 in the manner best shown in FIGS.15, 17 and 18, and hereinafter described in connection with thosefigures.

In FIG. 6 of the drawings, I have illustrated alternative means forintroducing the fresh air into the exhaust line, wherein the air ispre-heated to increase the efficiency of oxidation of hydrocarbons andcarbon monoxide in the system. This preheating is desirable as theefficiency of the catalyst bed decreases after the apparatus has beenemployed for a considerable period of time.

The air is pumped from air pump 16 through conduit 98, which maycomprise a copper tube similar to conduit 18 in FIG. 1 for the portionthereof that is external to the catalyst case and the exhaust pipe, butwhich is preferably composed of alloy steel tubing for the portionthereof that is within the catalyst case and the exhaust pipe. A checkvalve 100 is preferably included in conduit 98, and may be associatedwith the air pump outlet port as described in connection with FIG. 1..Conduit 98 extends through the wall of catalyst case 34 near the rearend of case 34, and may be coiled within the small rear chamber 102between the rear head 58 and the catalyst bed, conduit 98 thu forming aheating coil 104 in the rear portion of the catalyst case. Conduit 98then extends forwardly through the catalyst case and through the exhaustpipe, so that its outlet end 106 will be positioned near the connectionbetween exhaust pipe 14 and exhaust manifold 12. In this manner, heatwill be transferred to conduit 98 and to the air therein from both theexhaust pipe and the catalyst bed.

In FIGS, 11, 12, 13 and 14, I have illustrated an alternative embodimentof my catalytic reactor which employs a plurality of porous ceramicblocks which are impregnated throughout with the active catalyticmaterial. Referring at first to FIGS. 11, 12 and 13, the ceramic blocks108 are preferably provided in a flat oval shape with axis dimensions ofabout 4 /2 inches high and about 9 inches wide, with an axial depth orthickness of about 2 to 2 /2 inches. It will be noted that thecross-sectional area of these porous blocks is somewhat smaller than thecorresponding cross-sectional area of the catalyst bed 68 where theparticulate catalyst is employed, a best shown in FIGS. 3, 4 and 5. Thesmaller size is permitted by the increased efficiency of the porousceramic block catalyst. Even with this reduced size, the ceramic blockcatalyst will have many times the effective catalyst surface areatherein as compared with the particulate catalyst without having a backpressure any greater than that normally encountered in a conventionalmufiler, and will therefore function more efliciently and for a longerperiod of time than the particulate catalyst. This greatly increasedsurface area in the porous ceramic catalyst is permitted because the webpartition walls within the ceramic blocks may be provided with athickness of about 0.020 inch or less, whereby the entire supportingceramic material throughout the blocks may be impregnated with catalyst,substantially all of the catalyst being usefully exposed within a depthof about 0.010 inch or less on opposite sides of these thin webpartition walls.

The ceramic catalyst blocks are preferably constructed from claymaterials normally used for making ceramic brick or porous porcelains,and are usually formed by soaking the ceramic slip into a carbonaceousor organic porous structure, removing the excess slip from the structureby squeezing or alternatively by blowing with air, or sucking by vacuum,leaving the slip in a thin layer on the porous structure, so that upondrying and firing at a temperature on the order of about 2000 F. thethickness of the membranes of ceramic material remaining after burningout the carbonaceous or organic porous structure will be approximately0.020 inch or less. This results in rigid, non-shrinkable structureshaving the desired high porosity and thin partition walls. Nevertheless,because of the very thin honeycomb walls throughout the blocks, they arerelatively fragile, and it is accordingly desirable to provide areinforcing ceramic layer 110 of reduced porosity and increased strengthabout the periphery of each of the blocks. This peripheral layer 110 maybe made by painting each block around its edge surface with an'airhardening cement such as Sourisen or Harwaco bond, or may be provided inthe original manufacture of the blocks by incorporating less or noburnout material in the peripheral edges.

According to another procedure for making the blocks, the mixture ofminerals usually used for ceramic purposes, such as feldspar, fire,china and ball clays, nepheline synite, and the like, is mixed with aburnout material such as cork, sawdust, wood flour, grass, straw,petroleum tar or the like, as is used in making lightweight insulatingbrick. However, for the present purpose, the burnout content isincreased over that used in making conventional lightweight insulatingbrick, and the burnout material may be oriented primarily with thelength of the burnout material arranged in the direction of gas flow,that is, through the 2-2 /z inch axial width of the blocks, so as toprovide maximum porosity in the direction of gas flow to aid pressuredrop, while retaining adequate structural strength.

The active catalytic chemicals embodied in the ceramic block type ofcatalyst are the same as those described above in detail in connectionwith the particulate catalyst. The clay material can be mixed with thesalts of the impregnating catalytic materials as the blocks areoriginally pressed to shape or extruded, and after completion of firing,the active catalytic material will constitute a major portion of thehoneycomb walls in the blocks. Salts of the desired multi-valent metalelements will be oxidized upon firing to provide the desired metal oxidecatalyst composition in the blocks, such as ferric oxide, chromic oxideand copper oxide. If the activity of the catalyst in the walls is lowerthan desired, then the walls may be etched with acid to better exposethe catalyst, and then reactivated by heating.

An example of one procedure which I have followed in producing thecatalyst blocks is as follows: Iron rouge and water were added to a clayslip mixture normally used for porous ceramics. The final mixture, byweight, was 34.5% clay components, 20.2% iron rouge (Fe O and 55.3%water. This clay-iron slip was placed in a suitable container into whichvinyl sponges were immersed. The sponges were Worked under the slipuntil soft and saturated, after which the sponges were squeezed as dryas possible. These sponges were then slowly dried with mild heat under aheat lamp. After drying the sponges were placed in a kiln and fired to1900 F. All of the vinyl sponge material was consumed and burned,leaving rigid clay bricks impregnated throughout with the iron oxide.The resulting bricks were of excellent porosity, were of good strength,and were brown in color from the iron oxide.

The bricks were then immersed in a solution of chromic acid of 12%.%strength by weight, and subsequently dried and activated at 600 F.changing the chromic acid to chromic oxide, and through reaction withthe iron in the ceramic, also converting some chromic acid to ironchromate. The final brick comprised 56% ceramic, 32% iron oxide and 12%chromic oxide. The density of the brick per cubic foot was 30 pounds.The partition wall thicknesses throughout the brick were about 0.020inch, with a mean pore diameter on the order of about 0.040 inch.

The blocks thus produced are then trimmed to accurate dimensions, and anair drying cement painted around the oval edge of each block, thiscement hardening so as to eggshel the blocks against edge damage.Although I have thus obtained satisfactory results by employing vinylsponges for the carbonaceous or organic porous structure which is burnedout during firing of the blocks, I prefer to employ a plastic spongematerial which has larger pores, and which will therefore result infinished catalytic blocks of greater porosity, causing reduced exhaustback pressure, than those resulting from the use of vinyl sponges. Ihave found that polyurethane ester sponge with large holes has pores ofabout the right size, but that these pores are preponderantly closedwith very thin membranes, referred to in the plastic art as flaps, whichextend across the plastic web in the sponge. If these flaps were left inpolyurethane ester sponges employed for producing my porous ceramicblocks, the resulting blocks would produce an untenably high backpressure in operation. However, by squeezing the polyurethane estersponges While immersed in a suitable solution for a short period of timethese flaps can be dissolved to the desired extent, without substantialeating of the web plastic, providing sponges which, after subsequentceramic impregnation and firing, result in highly porous ceramic blockswhich produce very low exhaust back pressure.

An example of a procedure which has proven effective for removingsubstantially all of these flaps in polyurethane ester sponges is toimmerse and squeeze the sponges for 2 minutes in a sodium hydroxidesolution of 25% strength by weight at a temperature of F. Similarlyeffective defiapping resulted from immersion and squeezing of thesponges for 1 minute in the same solution at 200 F. Using polyurethaneester sponges thus prepared as the carbonaceous or organic porousstructure (which is later burned out) for forming the porous ceramicblocks, the resultant ceramic product gave a surprisingly low backpressure equivalent to only 1%. inches of water for a ceramic bed 12inches deep of 32 square inches cross-sectional area, with an exhaustgas flow of 50 cubic feet per minute. The ceramic webbing thus producedwas very good, the ceramic strong, and the surface for catalyticreaction was about tenfold the surface of the particulate catalyst inthe preferred particulate catalyst case 34 described above. The backpressure of the particulate catalyst bed in the case 34 at 50 cubic feetper minute exhaust gas flow is equivalent to about 7 to 9 inches ofwater. Further, the intricate ceramic web or" this product is effectiveto trap any lead oxide or road silt in the first brick or two, leavingthe subsequent bricks clean for the catalytic reaction.

By reducing or eliminating the step of squeezing the polyurethane estersponges during the detlapping, some of the flaps can be retained in thesponges, which will increase the interval surface area of the porousceramic blocks produced. This may be done while still keeping the backpressure within acceptable limits.

It is to be understood that the foregoing defiapping procedure is givenmerely as an illustration of one suitable procedure, and it will beobvious that variations in the solution, temperature and timing may beemployed with similar results. It is to be noted that prolongedimmersion in the 25 by weight sodium hydroxide solution at roomtemperature was ineffective for removing the flaps, while immersion for8 minutes at 200 F. not only removed the fiaps but almost completely atethe remaining Web.

Tests on sponges of the companion plastic, polyurethane ether (a morecommon variety of the polyurethane group) showed that sponges of thismaterial were more resistant to defiapping, requiring immersion in thesame 1siolution at 200 F. for at least 10 minutes to remove the aps.

While it is obvious that a very wide variety of ceramic slip formulasmay be employed, and the present inventron is not in any way limited toany particular formula, an example of a slip formula, with catalyticcomponents 21 included, which has provided good results with thepolyurethane ester sponges is approximately as follows:

Percent Tennessee ball clay 9.1 California kaolin 9.1 Plastic vitrox13.7 Talc 27.6 Iron oxide rouge 30.5 Copper oxide 10.0

Total solids 100.0

To these solids was added 28.5% (of the weight of the solids) of watercontaining small quantities of sodium silicate, soda ash and vitrofoss.The amounts of these last ingredients included with 65.8 pounds of thesolids were 160 cc. of 25% solution of sodium silicate, 77 cc. of sodaash solution and 350 cc. of 10% vitrofoss. The foregoing slip mixtureweighs 63% ounces per quart.

While there is nothing significant or exact in the above slip formula,it has shown that this general type of slip mixture provides thefollowing results: (1) a good ceramic with minor shrinkage and goodstrength, (2) good thinness so that when the plastic is squeezed, anydesired amount of ceramic slip remains (good blocks with a total weightas low as 10 pounds per cubic foot having been produced), (3) surfacetension of the slip such that no ceramic flaps blind the web or archover the holes, and (4) inclusion of the catalytic ingredients in theceramic formula (with the exception of the final addition of the chromicacid to etch and activate the surfaces).

These slip-impregnated plastic sponges are slowly dried, then fired toabout 400 F. to decompose or volatilize the plastic, and then fired tofrom 1900 to 2000" F. The drying and plastic firing steps are preferablytaken slowly so that abnormal volatilization does not rupture theceramic texture, but after these two steps have been passed, the firingcan be conducted quite rapidly.

Another example of a procedure for producing the catalyst blocks is tomix fire clay with straw and a binder, including in this mixture aquantity of ferric sulfate which will yield about 6 lbs. per cubic footof ferric oxide upon firing. Also included may be other ingredients suchas chromic acid and copper sulfate which will produce chromic oxide andcopper oxide upon firing. The sulfate content of the ferric sulfate,upon heating, liberates sulfur dioxide gas, causing a frothing andswelling of the fire clay. The straw burns and further aids the porosityof the final block, and with the straw being generally axially directedin the original pressing, when the straw is burned out it will leaveaxial pores through the blocks of the desired size, as given by the sizeof the straw. When the blocks have been fired and cooled, they are thentrimmed and painted about the oval edge with an air dry ing cement toeggshell the blocks against edge damage.

An alternative method of fabricating the porous ceramic blocks is toproduce the blocks without including the salts of the final catalystoxides, and then, after completion of the blocks, to soak the solutioncontaining the impregnating salts thoroughly throughout the blocks. Thissoaking is preferably accomplished by boiling, or by prior evacuation ofthe blocks to remove air. Then, the water of solution is slowlyevaporated so that the salt will remain upon the honeycomb walls. Theblocks are then fired so that the salts will decompose to the catalystoxides, or, alternatively, the salts may be reacted with ammonium gas orammonium hydroxide. The blocks are then water-washed and dried.

The completed block are then placed in a catalyst case 112 by rollingthe case shell 114 around the blocks with the blocks laid side-by-side.It is preferable to space the consecutive blocks slightly apart topermit crimping of the case shell 114 between adjacent blocks to formshallow intervening ribs 116. These crimped ribs 116 serve to seal eachblock in place so that gases of surface area.

in the porou block type of catalyst has the further 22 will not by-passaround the blocks, which is particularly important in the event of anyshrinkage of the blocks. The ribs 116 have the further advantage that ifone block is damaged, it will be self-contained. Also, by thusseparating the individual blocks, gas diffusion will occur between theblocks, retarding possible channeling of the exhaust gases.

Although the catalyst case shell 114 may be insulated, if desired, thisis not necessary with my preferred porous blocks because of theextremely low heat conductivity of the blocks, and because the cemented,non-adsorptive peripheral edges of the blocks serve as an insulatingmedium.

As with the particulate catalytic case, it is desirable to support theheat resistant protective disc or button 71 centrally within the ceramicblock catalyst case 112 in the combustion chamber ahead of the firstblock 108, to throw out as much as possible of the particulate leadoxide so as to protect the following catalytic surfaces in the blocks.

The catalytic case 112 is completed by front and rear end heads 11S and120, respectively.

The performance of my porous ceramic catalyst is much higher than thatof the particulate catalyst in view of the greatly increased effectivesurface area. While the eifective surface area of the particulatecatalyst bed is on the order of about sq. ft., the effective area of theporous block type of catalyst is on the order of about 400 sq. ft. orhigher. If desired, by decreasing the thickness of the partition wallsthis effective surface area within the block catalyst bed can beincreased to as much as about 1,000 sq. ft. This provides a much longereffective life for the block type of catalyst, as the life of thecatalyst is directly dependent upon the amount This greatly increasedsurface area advantage of a greatly increased capacity of the catalystfor poisons without serious decrease of catalytic eifect. The porousblocks also have a greater filtering effect than the particulatecatalyst, thus further assisting in the removal of poisons in theforward part of the catalyst bed, leaving a substantial portion of thecatalyst bed substantialy undamaged by poisons.

It is to be noted that if desired, the particulate type of catalyst maybe composed of porous particles similar in composition to the porousceramic blocks, but the blocks appear to be preferable due to theirgreater strength and resistance to damage from abrasion.

In FIGURE 14 I have illustrated a catalyst case 122 which containsmodified front and rear porous catalyst blocks 124 and 126,respectively. The front block 124 has a conical forward portion 128,while the rear block 126 has a complementary conical recess 130 at itsrear end. The conical shape of the forward block 124 provides the sameadvantage as the conical forward portion of the particulate catalystbed, namely, to provide quick heating so as to give a kick-off to thecatalyst reaction, and to cause turbulence of the entering gases.However, the heat capacity of the porous block type of catalyst is solow that this forward cone is not necessary, to give the desired initialkick-off to the catalyst reaction, and a flat forward surface on thefront block as shown in FIGURE 11 produces excellent results. Ifdesired, where the front block has a flat forward surface, a deflectorcone (not shown) may be employed forward or upstream of the entering gasinlet to provide the desired turbulence of the entering gases. As in thecase of the particulate catalyst, the complementary rear conical recess130 causes the catalyst bed depth to be uniform across its entirecross-sectional area. Although the ceramic disc or button has not beenshown in FIG- URE 14, it may be employed in front of cone tip of block124, if desired.

In FIGURES 15-22, inclusive, I have illustrated a slipclutch drive airpump which I have found suitable for providing the required amount ofair [for] in my system for the varying engine speeds, under idling, lowspeed and high speed driving conditions, and in particular for the fourprincipal modes of vehicle operation, idle, acceleration, decelerationand cruise. The details of construction of the air pump 16 shown inFIGURES -22, inclusive, do not form a part of my present invention, andit is to be understood that other types of variable drive means may beemployed in connection with my system [for providing only a moderateincrease in the air supply between idle engine speed and highway enginespeed], wherein slippage in the drive means increases with an increasein back pressure in the exhaust system and decreases with a reduction inthe back pressure.

The pump 16 includes a base member 132 upon which a pair of end plates134 and 136 are mounted by means of bolts 137 or by other suitablemeans. A cylindrical pump case 138 is supported between end plates 134and 136 by screws 140 to provide a sealed pumping chamber therein.

Pump inlet ports 142 are provided in end plates 134 and 136 adjacent topump case 138, and receive air through respective inlet passages 144.Suitable air filters and air silencers 146 are disposed in the inletpassages 144, and passages 144 open to the atmosphere through openings148 in the base member 132 or horizontally through openings in endplates 134 and 136.

Air outlet port 150 is provided through end plate 136, and communicateswith the air conduit 18.

t will be noted that by providing my inlet ports 142 and outlet port 150in the end walls rather than in the cylindrical pump case as is theusual procedure, I greatly reduce frictional wear on the ports, and onthe pumping vanes, as the ports are not in the area of centrifugallyforced engagement of the vanes against the pump case.

Pump shaft 152 is rotatably mounted in sealed antifriction bearings 154which are supported in the respective end plates 134 and 136, and pumprotor 156 is keyed to shaft 152 within pump case 138 between end plates134 and 136 so as to rotate with shaft 152. Pumping vanes 158 areradially slidably mounted in rotor 156 so as to be engaged in slidingcontact with the inner wall of pump case 138, by centrifugal force.

The pump shaft 152 is driven through a circular clutch plate 160 that ismounted on a threaded spindle 162' on one end of pump shaft 152, plate160 being held in position by nut 164.

Clutch plate 160 is disposed within a clutch housing 166 which is drivenby the engine fan belt 22, housing 166 including a pulley portion 168having an annular recess 170 thereinfor receiving the fan belt 22.Clutch housing portion 168 is rotatably mounted on an antifrictionbearing 172 which is supported on a fixed hub 174 extending outwardlyfrom end plate 134 and which is retained on hub 174 by a suitableretaining ring. The I pulley portion 168 is tapped in several locationsnear the periphery to accept screws which clamp and retain clutchhousing 166 to pulley portion 168.

Clutch housing 166 also includes an intermediate housing member 176 anda housing cover member178, cover member 178 preferably being finned forcooling purposes and including an axial cup or thimble portion180.having a grease reservoir 182 therein. Upon rotation of the clutchhousing 166, grease disposed therein frictionally engages the clutchplate 160 so as to rotate clutch plate 160 and pump shaft 152. Acombination of a proper grease in clutch housing 166 and a clutch plate160 of the particular construction shown in the drawings and hereinafterdescribed in detail produces relatively low slippage between clutchhousing 166 and clutch plate 160 [at low speedsj when the back pressurein the exhaust system is relatively low, and a large amount of slippage[at high speeds] when the back pressure is 34 relatively high, thusproviding the desired air output formy apparatus.

The clutch plate is provided with a plurality of circularly arrangedopenings 184 therethrough, preferably six in number, the openings 184preferably being spaced at equal radial distances from the center ofclutch plate 160. A channel recess 186 extends from each opening 184. tothe. periphery of clutch plate 160 on one side of clutch plate 160, therecesses 186 extending to a depth of approximately one-third thevthickness of the clutch plate. Similar channel recesses 188 on the otherside of clutch plate 166. extend from the respective openings 184 to theperiphery of the clutch plate. 186 from each opening 184 will overlapthe channel 188 from an adjacent opening 184, but they will notbreak-out into each other since the respective depth of each is onlyone-third the total thickness of clutch plate. 160. A relatively smallclearance exists on both sides of clutch plate 169, and a largerclearance exists on the outer edge between clutch plate 160. and clutchhousing 166. Grease within clutch housing 166 is then pumped orcirculated by clutch plate 160 through the channels 186 and 18S,utilizing the larger clearance between the outer edge of clutch plate169 and clutch housing 166 as a reservoir for the grease in transit,limiting the tendency to increase frictional engagement at this pointduring high speed operation.

A high temperature silicone grease has been found satisfactory for usein the clutch housing, providing an increase of from about 1 /2 to 2cubic feet per minute to about 5 cubic feet per minute of pump airoutput for an engine speed range of from about 450 rpm. (idle speed) toabout 2500 rpm. (highway speed). Variations in this relationship betweenpump air output and driven speed of the pump may be accomplished byVarying the amount of side clearance of the clutch plate 160 in clutchhousing 166, which is preferably within a range of from about 10 toabout 50 thousandths of an inch, and by controlling the thickness orcentipoise of the grease employed.

It is preferred to employ a type of grease which will have thecharacteristic of thixotrophy; that is, one which will functionprincipally as a solid until a certain shear point is reached, andthereafter will function primarily as a liquid. Silica which is powderedto a fineness of less than one micron in particle size exercises thisproperty when mixed with a suitable carrier liquid such as water or oil.Other materials which will perform in this manner are finely powderedSantocel produced by Monsanto Chemical Company and finely powderedKaolin produced by Minerals and Chemicals Corporation. Finely powderedsilica appears to be preferred as it does not attrite by grindingitself. Also very small concentrations of Guar, such as Jaguar, acommercial gum resin, will promote thixotrophy, so that small quantitiesof such material may be employed.

I find it convenient to mount the interrupter points 96 on the outsideof pump end plate 136, and to provide a multilobed cam member 192 on theend of pump shaft 152 which projects outwardly through end plate 136 forproducing the vibratory motion required for the interrupter points 96.In practice it has been found that asingle-lobed cam member will heatthe coil abnormally at low speeds of car operation. By providing a threelobed cam member 192, and by driving the pump 16 at twice the speed ofthe engine, a spark frequency of six per engine revolution is achieved,which is consistent with a six-cylinder engine distributor, thuspreventing such abnormal coil heating and providing a good steady sparkeven at low or idle engine speeds.

The points 96 include amovable contact member 194 and a fixed contactmember 196, the movable contact member 194 being spring biased againstthe cam member 192 to provide the desired interruption of the points.

The purpose of interrupter points 96 is to provide a The channel[s]-"means of interrupting the direct current to the primary winding of theconventional automotive ignition coil 92, enabling the coil to thenstep-up the primary voltage to a secondary voltage sufficient to firethe ignition spark plug 36 as previously described. A typicalinstallation would find fixed contact member 196 electrically groundedto pump end plate 136, and movable contact member 194 insulated from endplate 136, and [conected] connected externally to the primary coilwinding. A capacitor may be used across interrupter points 96 ifdesired, both for the elimination of metal transfer and for the moresatisfactory operation of the ignition system previously described.

In FIGURE 22 I have illustrated a mechanical regulating device which mayoptionally be employed for further limiting the pump output volume. Thisincludes a bore 198 extending downwardly through pump end plate 136 fromoutlet port 150 to the edge of end plate 136, with another passage 200connecting inlet port 142 with the bore 198 intermediate its ends. Aplunger 202 is slidable within bore 198, plunger 202 being attached toone end of a coil spring 204 positioned within bore 198 below plunger202. The lower end of spring 204 is connected to an adjusting screw 206which is threadedly engaged in the lower end of bore 198, extending outof bore 198 to permit adjustment thereof. A lock nut 208 may be providedon the exposed portion of adjusting screw 206.

In operation, when the engine and pump speeds are relatively low so thatthe pressure at outlet port 150 is correspondingly low, the plunger 202is biased upwardly by spring 204 to a position in bore 198 whereinplunger 202 seals off passage 200, so that the entire air output of thepump will be provided to the exhaust stream. When the engine and pumpspeeds are increased, the back pressure at the pump outlet port 150increases due to the increased pressure in the exhaust system, thusurging plunger 202 downwardly against the force of spring 204. When theengine and pump speeds increase sufficiently to raise the pressure atoutlet port 150 beyond a predetermined level, the plunger 202 will movedownwardly a sufiicient amount to permit the excess air output of thepump to be by-passed through bore 198 and passage 200 to inlet port 142.The amount of this recirculation of air from the outlet port back to theinlet port may be adjusted by shifting the position of adjusting screw206, thereby controlling the output volume of the pump which goes to theexhaust system to approximately the desired amount [(such as 2 cubicfeet per minute for a 235 cubic inch displacement engine)], even whenthe engine is operating at high speeds.

The regulator shown in FIGURE 22 is merely one suitable device forcontrolling the pump output volume, and it will be appreciated thatother means may be employed to accomplish this purpose. For example, thepressure relief valve may merely be vented to the atmosphere instead ofrecirculating the excess air output back to the inlet port, althoughreturning the air to the inlet port has the advantages of minimizingnoise of the air relief and of providing pre-filtered air to the pumpinlet. Another means for regulating the pump output volume would be togradually close the inlet or suction ports of the pump in response tooutput pressure to starve" the input of [By thus providing a combinationof both the slipclutch and output pressure regulating means, atrelative- 1y low engine speeds, the pump can run at moderate speedsgiving full output to the exhaust system, but as the speed increases andthe back pressure hkewise increases, then although the moderately higherpump speeds permitted by the slip-clutch will cause more air to bepumped, this excess will be dissipated by the regulator, thusmaintaining close to the desired air throughput level] Since the outputpressure regulator only limits the air when the exhaust back pressuregoes above a predetermined value, it will not interfere with therelatively large percentage of air provided by the pump during the idleand deceleration modes when back pressure is low. Thus, if the pressureregulator is employed it will only be effective to limit the air outputto a fixed value under conditions of maximum back pressure when theoutput is already being limited by slippage of the slip-clutch inresponse to back pressure in the exhaust system. Such conditions may bepresent during acceleration or at high vehicle speeds. Proper adjustmentof the output regulator will prevent it from interfering with operationof the slip-clutch drive in response to back pressure as set forthhereinabove during most driving conditions. If desired, the outputregulator may becompletcly eliminated since the slip-clutch providesadequate back pressure-responsive control of the air supply for normalvehicle operation.

While the instant invention has been shown and described herein in whatis conceived to be the most practical and preferred embodiment, it isrecognized that departures may be made therefrom within the scope of theinvention, which is therefore not to be limited to the details disclosedherein, but is to be accorded the full scope of the claims.

What I claim is:

1. Apparatus for removing impurities from an internal combustion engineexhaust system which comprises: an exhaust conduit, air pumping meansconnected to and communicating with the inside of said exhaust conduitto provide a mixture of air and exhaust ingredients, said air pumpingmeans including a slip clutch the operation of which determines thevolume of air introduced into said exhaust conduit, said air pumpingmeans and said slip clutch being operable by said engine with anincrease in speed of said engine increasing the slippage of said slipclutch, and decreasing engine speed effecting a decrease in slippage ofsaid slip clutch, producing a ratio of air to exhaust ingredientsdiminishing with an increase in slippage of said slip clutch andincreasing with decreasing slippage of said slip clutch, direct ignitionmeans in said exhaust conduit downstream of said air pumping means forigniting exhaust ingredients not previously oxidized; and catalyticoxidizing means including a catalyst bed, the catalytic means beingconnected to said exhaust conduit downstream of said direct ignitionmeans for oxidizing exhaust ingredients not previously completelyoxidized.

2. In a combination of an internal combustion engine, an exhaust systemdirectly associated with said engine and embodying exhaust conduit meansproviding a closed path of flow of exhaust ingredients from thecylinders of the engine to a mufiier, said system developing a backpressure varying under differing engine operating conditions and havinga zone therein within which oxidation promoting conditions obtain foroxidizing exhaust ingredients not previously completely oxidized, andmeans including an air pump for introducing air into said exhaust systemat a point where said air will improve the oxidation promotingconditions in said zone, the improvement which comprises a slip clutch.operatively connecting the engine to said air pump for driving the pump,said slip clutch being responsive to back pressure in said exhaustsystem whereby under relatively low back pressure said slip clutchoperates said pump for delivery of a relatively large percentage of airin relation to the exhaust volume and under relatively high backpressure said slip clutch operates said pump for delivery of arelatively small percentage of air in relation to the exhaust volume.

3. Apparatus as defined in claim 2, wherein said muffler is a catalyticmufiler and said zone is defined by a catalyst bed in the catalyticmuffler.

4. Apparatus as defined in claim 2, wherein said zone comprises meanswithin said exhaust system whereby temperature is produced suficientlyhigh to cause direct ignition of said exhaust ingredients.

patent.

References Cited by the Exanfiner The following references, cited by theExaminer, are of record in the patented file of this patent or 'theoriginal UNITED STATES PATENTS 23 Rohde 123-169 Finn 23-234 Penn 123-169Spase et a1 230-271 XR Lentz 313-115 Smits 313-131 Nutt 230-270 XCalvert 60-30 Cornelius 60-30 Ridgeway 60-30 Schafier et a1. 60-30Ridgeway 60-30 JULIUS E. WEST, Primary Examiner. 15 EDGAR W. GEOGHEGAN,Examiner,

